Climate

Byers, H. R., and R. K. Hall, 1955: A census of cumulus-
cloud height versus precipitation in the vicinity
of Puerto Rico during the winter and spring of
1953–1954. J. Meteor., 12, 176–178.

Abstract:

The analysis of fifteen cloud-census flights confirms the common existence of warm precipitation from trade-wind cumuli. A probability that over-water clouds of certain vertical developments will contain precipitation is presented. Since the examined over-water clouds with tops higher than 11,500 feet always contained precipitation and yet were well below the freezing level, the futility of initiating rain by seeding clouds with freezing reagents becomes obvious.

Spatially explicit climate data contribute to watershed resource management, mapping vegetation type with satellite imagery, mapping present and hypothetical future ecological zones, and predicting species distributions. The regression based Parameter-elevation Regressions on Independent Slopes Model (PRISM) uses spatial data sets, a knowledge base and expert interaction to generate GIS-compatible grids of climate variables. This study applied PRISM to generate maps of mean monthly and annual precipitation and minimum and maximum temperature for the Caribbean islands of Puerto Rico, Vieques and Culebra over the 1963-1995 averaging period. PRISM was run under alternative parameterizations that simulated simpler interpolation methods as well as the full PRISM model. For temperature, the standard PRISM parameterization was compared to a hypsometric method, in which the temperature/elevation slope was assumed to be -6.5°C/km (HYPS). For precipitation, the standard PRISM parameterization was compared to an inverse-distance weighting interpolation (IDW). Spatial temperature patterns were linked closely to elevation, topographic position, and coastal proximity. Both PRISM and HYPS performed well for July maximum temperature, but HYPS performed relatively poorly for January minimum temperature, due primarily to lack of a spatially varying temperature/elevation slope, vertical atmospheric layer definition, and coastal proximity guidance. Mean monthly precipitation varied significantly throughout the year, reflecting seasonally differing moisture trajectories. Spatial precipitation patterns were associated most strongly with elevation, upslope exposure to predominant moisture-bearing winds, and proximity to the ocean. IDW performed poorly compared to PRISM, due largely to the lack of elevation and moisture availability information. Overall, the full PRISM approach resulted in greatly improved performance over simpler methods for precipitation and January minimum temperature, but only a small improvement for July maximum temperature. Comparisons of PRISM mean annual temperature and precipitation maps to previously-published, hand-drawn maps showed similar overall patterns and magnitudes, but the PRISM maps provided much more spatial detail

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Aircraft measurements of ozone, methane, carbon monoxide, relative humidity, and equivalent potential temperature were performed during the TROPOZII campaign. During the aircraft descent down to Pointe-á-Pitre (16.3°N, 61.5°W), at 2100 UTC on January 12, 1991, two ozone peaks (75 ppb) are observed, one at an altitude of 7.5 km and the other at 3.0 km. A physicochemical interpretation for each ozone peak is proposed in connection with the meteorological context, using radiosounding data, total ozone content from TOMS/NIMBUS 7 and diagnoses issued from analyses by the European Centre for Medium-Range Weather Forecasts, Reading, England. The stratospheric origin of the 7.5-km ozone peak is inferred from negative correlations between ozone and its precursors and from diagnoses based on potential vorticity and ageostrophic circulations depicting the structure of the tropopause fold embedded in the subtropical jet front system. Using an appropriate method to isolate cross- and along-front ageostrophic circulations, we show that much of the observed structure of the tropopause fold can be ascribed to transverse and vertical circulations associated with the irrotational part of the flow. Though the downward extent of the subtropical tropopause fold (400 hPa) is restricted in comparison with typical extratropical tropopause ones (700 hPa), the present results suggest that subtropical tropopause folds may significantly contribute to the global stratosphere-troposphere ozone exchange. The origin of the 3.0-km ozone peak trapped just below the trade wind inversion cannot be ascribed precisely. Analogies with other measurements of dust and aerosols transported over the Atlantic or Pacific in the summer season are discussed. Various possibilities are examined: (1) an earlier stratospheric intrusion event, (2) long-range transport by the trade winds of biomass burning species emitted over West Africa, and (3) fast photochemical ozone formation occurring just below the trade wind inversion within already polluted air parcels originating from remote regions (United States and Gulf of Mexico) after eastward and southward transport around the western Atlantic anticyclone.

Geographical regions of covariability in hourly precipitation over the island of Puerto Rico are exposed using factor analysis. It is argued that the data are consistent with a common factor model when an orthgonal rotation is applied to the factor loading matrix. The results suggest that Puerto Rico can be divided into six regions, with each region having a similar covariance structure of summer season convective rainfall. The six regions can be grouped into a western area and an eastern area based on contrasting diurnal rainfall signatures. The study is the first step in developing improved forecast guidance for precipitation over the island. It is believed to be one of the first studies attempting geographical regionalization of precipitation on the convective scale.

The science of water is an endless world
for scientific research and creativity, in the
water all the needs converge, the feelings
and human traditions, water is the origin of
life and its sustain, water is food supply, and
it is also a base of the culture, traditions and
religions; and, unfortunately, the cause of
diverse conflicts among people and countries.
Water is a renewable, but finite resource,
endangered in many places by its non-rational
use, in such a proportion, that the unmeasured
disposal of pollutants in the water bodies or
its exploitation over its natural capacity of
renewal, might also put at risk its condition of
renewable resource. Water is under the threat
of climatic change that will affect its spatial and
temporal distribution in a negative way in every
place. The environmental situation of Latin America
and the Caribbean is fragile, and particularly
in relation to water many threats exist that
justify the need of urgent actions. The intensive
deforestation in the tropical forest and woods
from temperate and cold regions; the modification
or destruction of coastal ecosystems, the high
degree of erosion due to inadecuated agriculture
practices and incorrect use of the soil; the
indiscriminated use of chemical and synthetic
products in agriculture and urban industries;
integrated to global environmental problems,
among them, climate change and the ozone
layer depletion, are being felt in different degrees
in various parts of the continent. An evaluation
of the Forum of Ministries of Environment in
Latin America and the Caribbean, carried out in
Bridgetown, Barbados, in 2000, recognized the
continuation of the environmental deterioration
in the region and in analizing the problem of
water, the following were indicated among the
main problems:

We excluded throughfall from humid tropical forests in Puerto Rico
for a period of three months to determine how drought affects
greenhouse gas emissions from tropical forest soils. We
established five 1.24 m2 throughfall exclusion and five control plots
of equal size in three sites located on ridges, slopes, and an upland
valley dominated by palms (total of 30 plots). We measured weekly
changes in carbon dioxide (CO2) and bi-weekly changes in nitrous
oxide (N2O) and methane (CH4) in response to manipulation. We
additionally measured the effects of throughfall exclusion on soil
temperature and moisture, nutrient availability, and pH. Rainout
shelters significantly reduced throughfall by 22 to 32 % and
decreased soil moisture by 16 to 36% (top 10 cm). Rates of CO2
emissions decreased significantly in the ridge and slope sites (30%,
28%, respectively), but not the palm during the experimental
drought. In contrast, the palm site became a significantly stronger
sink for CH4 in response to drying (480% decline relative to
controls), while CH4 fluxes in the ridge and slope sites did not
respond to drought. Both the palm and ridge site became a sink for
N2O in response to drought and the slope site followed a similar
trend. Soil pH and available P decreased significantly in response
to soil drying; however, available N was not affected. Variability in
the response of greenhouse gas emissions to drought among the
three sites highlights the complexity of biogeochemical cycling in
tropical forested ecosystems, as well as the need for research that
incorporates the high degree of spatial heterogeneity in
experimental designs. Our results show that humid tropical forests
are sensitive to climate change and that short-term declines in rainfall could result in a negative feedback to climate change via
lowered greenhouse gas emissions and increased greenhouse gas
consumption by soils.

Cloud water, rainwater, and aerosol particles were collected in Puerto Rico from
December 2004 to March 2007 in order to investigate their chemical composition,
relation to sources, and removal processes. The species analyzed were inorganic ions,
metals, total and dissolved organic carbon (TOC, DOC), total nitrogen (TN), and organic
acids. For all samples, the dominant species were marine (Na+, Cl−), representing about
50%–65% of total content. Non‐sea‐salt fraction was dominated by SO42− (17%–25%),
followed by water‐soluble organic (2%–8%) and total nitrogen (2% –6%) compounds.
Organic acids represented contributions to the organic fraction in cloud water of 20%
and 6% for aerosol particles. Inorganic species were predominant in total nitrogen portion.
The chemical composition of cloud water, rainwater, and aerosol particles were observed
to be sensitive to transport patterns. Air masses from northwest Africa showed the highest
concentrations of nss‐Ca2+, Fe, and Al, suggesting a crustal origin. The pH values for
cloud water and rainwater observed under this transport pattern were higher than
background conditions, probably due to the alkalinity associated with nss‐Ca2+. The
highest concentrations of Cl− and SO42−, with lower pH, were measured during periods
of influence from Soufriere Hills volcano eruptions, most likely due to emitted SO2 and
HCl. Air masses from North America had an anthropogenic influence, where levels of
nss‐SO42−, TOC, and TN were higher (∼4 times) than in clean air masses. These results
suggest that long‐range transport could be an extra source of metals and organic/nitrogen
species to the Caribbean region ecosystems.

Approximately half of the tropical biome is in some stage of recovery from past human disturbance, most of which is in secondary forests growing on abandoned agricultural lands and pastures. Reforestation of these abandoned lands, both natural and managed, has been proposed as a means to help offset increasing carbon emissions to the atmosphere. In this paper we discuss the potential of these forests to serve as sinks for atmospheric carbon dioxide in aboveground biomass and soils. A review of literature data shows that aboveground biomass increases at a rate of 6.2 Mg ha−1 yr−1 during the first 20 years of succession, and at a rate of 2.9 Mg ha−1 yr−1 over the first 80 years of regrowth. During the first 20 years of regrowth, forests in wet life zones have the fastest rate of aboveground carbon accumulation with reforestation, followed by dry and moist forests. Soil carbon accumulated at a rate of 0.41 Mg ha−1yr−1 over a 100-year period, and at faster rates during the first 20 years (1.30 Mg carbon ha−1 yr−1). Past land use affects the rate of both above- and belowground carbon sequestration. Forests growing on abandoned agricultural land accumulate biomass faster than other past land uses, while soil carbon accumulates faster on sites that were cleared but not developed, and on pasture sites. Our results indicate that tropical reforestation has the potential to serve as a carbon offset mechanism both above- and belowground for at least 40 to 80 years, and possibly much longer. More research is needed to determine the potential for longer-term carbon sequestration for mitigation of atmospheric CO2 emissions.